Defending the Earth!, formerly Who is Doctor Who?, was an Earth-run website originally created by Clive Finch to find the name of the Doctor, later controlled by Mickey Smith, and then by the mysterious David R.
History
Originally Who is Doctor Who? only contained a page with a grainy black-and-white photograph of the Ninth Doctor with block capitals underneath reading "Have you seen this man?" It was a page where readers submitted their sightings of the Doctor and a page with historical drawings and photographs of him.
Later, when Mickey Smith took over, during 2005 and 2006 he wrote articles about various events, including the 2005 Auton invasion of London, the attempt by the family Slitheen to destroy the world and Guinivere One's flight to Mars, amongst others.
In 2007, he changed the style of the website, renamed it Defending the Earth!, and added missions for the readers of his website to help him as he seemingly decided it was hard to do things all by himself, allowing the readers to help combat alien invasions.
When David R took over from Mickey after he was left in an alternate reality, the missions were replaced with games and a quiz was added to test the readers of the website about what he, Mickey, Clive, LINDA and various other groups had researched over the last few years. However, by the time of the Battle of Canary Wharf, the website was no longer being updated.
Behind the scenes
"Who is Doctor Who?" originally contained a "sightings" page, which during the active life of the site contained a web form with which users could submit their own "sightings" of the Doctor, under whichever name they wished. After a short delay (presumably time for vetting of the comments for suitability by the BBC's website operators), new sightings would be added to the page. Additional user-generated pages of this type were added for several episodes' updates to the site.
Amusingly, the basic purpose of the "sightings" page was essentially to allow the public to add events to the Doctor Who universe.